Transcutaneous electrical nerve stimulation
Encyclopedia
Transcutaneous electrical nerve stimulation (acronym TENS) is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes. TENS by definition covers the complete range of transcutaneously applied currents used for nerve excitation although the term is often used with a more restrictive intent, namely to describe the kind of pulses produced by portable stimulators used to treat pain. The unit is usually connected to the skin using two or more electrodes. A typical battery-operated TENS unit is able to modulate pulse width, frequency and intensity. Generally TENS is applied at high frequency (>50 Hz) with an intensity below motor contraction (sensory intensity) or low frequency (<10 Hz) with an intensity that produces motor contraction.
, 63 A.D. It was reported by Scribonius Largus
that pain was relieved by standing on an electrical fish at the seashore. In the 16th through the 18th century various electrostatic devices were used for headache and other pains. Benjamin Franklin
was a proponent of this method for pain relief. In the nineteenth century a device called the electreat, along with numerous other devices were used for pain control and cancer cures. Only the electreat survived into the twentieth century, but was not portable, and had limited control of the stimulus.
The first modern, patient-wearable TENS was patented in the United States in 1974. It was initially used for testing the tolerance of chronic pain
patients to electrical stimulation before implantation of electrodes in the spinal cord dorsal column
. The electrodes were attached to an implanted receiver, which received its power from an antenna worn on the surface of the skin. Although intended only for testing tolerance to electrical stimulation, many of the patients said they received so much relief from the TENS itself that they never returned for the implant.
A number of companies began manufacturing TENS units after the commercial success of the Medtronic
device became known. The neurological division of Medtronic, founded by Don Maurer, Ed Schuck and Dr. Charles Ray, developed a number of applications for implanted electrical stimulation devices for treatment of epilepsy, Parkinson's disease, and other disorders of the nervous system. Maurer founded Empi, Inc., in 1977, and in the late 1980s purchased the TENS product line from Medtronic.
Today many people confuse TENS with Electro Muscle Stimulation (EMS). EMS and TENS devices look similar, with both using long electric lead wires and electrodes. TENS is for blocking pain, where EMS is for stimulating muscles.
Scientific studies show that high and low frequency TENS produce their effects by activation of opioid receptors in the central nervous system. Specifically, high frequency TENS activates delta-opioid receptors both in the spinal cord and supraspinally (in the medulla) while low frequency TENS activates beta-opioid receptors both in the spinal cord and supraspinally. Further high frequency TENS reduces excitation of central neurons that transmit nociceptive information, reduces release of excitatory neurotransmitters (glutamate) and increases the release of inhibitory neurotransmitters (GABA) in the spinal cord, and activates muscarinic receptors centrally to produce analgesia (in effect, temporarily blocking the pain gate). Low frequency TENS also releases serotonin and activates serotonin receptors in the spinal cord, releases GABA, and activates muscarinic receptors to reduce excitability of nociceptive neurons in the spinal cord.
In palliative care
and pain medicine, TENS units are used in an attempt to temporarily alleviate neuropathic pain
(pain due to nerve
damage).
Some patients benefit from this approach, while others do not, depending on individual differences,
and pain threshold. Use of TENS causes cell death at the site of application and should not be used long term. The number of cells that die is insignificant and most patients heal without complaints. TENS is more effective at relieving chronic pain, whereas when used on new injuries it sometimes aggravates the pain. Further use is documented in the attached references: in obstetric
care, particularly in labour
;
knee pain;
lithotripsy or bladder-stone removal;
and limb pain.
A significant number of TENS machine brands have been targeted for use for labour pain, although a 1997 report of a study done by the University of Oxford
said that TENS "has been shown not to be effective in postoperative and labour pain."
TENS should not be used across an artificial cardiac pacemaker
(or other indwelling stimulator, including across its leads) due to risk of interference and failure of the implanted device. Serious accidents have been recorded in cases when this principle was not observed. A 2009 review in this area suggests that eletrotherapy, including TENS, "are best avoided" in patients with pacemakers or implantable cardioverter-defibrillator
s (ICDs). They add that "there is no consensus and it may be possible to safely deliver these modalities in a proper setting with device and patient monitoring", and recommend further research. The review found several reports of ICDs administering inappropriate treatment due to interference with TENS devices, but notes that the reports on pacemakers are mixed: some non-programmable pacemakers were inhibited by TENS, but others were unaffected or auto-reprogrammed.
On areas of numb skin/decreased sensation TENS should be used with caution because it's likely less effective due to nerve damage. It may also cause skin irritation due to the inability to feel currents until they are too high. There's an unknown level of risk when placing electrodes over an infection
(possible spreading due to muscle contractions), but cross contamination with the electrodes themselves is of greater concern. TENS should also be used with caution in people with epilepsy or pregnant women; do not use over area of the uterus as the effects of electrical stimulation over the developing fetus are not known.
History
Electrical stimulation for pain control was used in ancient GreeceAncient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
, 63 A.D. It was reported by Scribonius Largus
Scribonius Largus
Scribonius Largus was the court physician to the Roman emperor Claudius.About 47 AD, at the request of Gaius Julius Callistus, the emperor's freedman, he drew up a list of 271 prescriptions , most of them his own, although he acknowledged his indebtedness to his tutors, to friends and to the...
that pain was relieved by standing on an electrical fish at the seashore. In the 16th through the 18th century various electrostatic devices were used for headache and other pains. Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...
was a proponent of this method for pain relief. In the nineteenth century a device called the electreat, along with numerous other devices were used for pain control and cancer cures. Only the electreat survived into the twentieth century, but was not portable, and had limited control of the stimulus.
The first modern, patient-wearable TENS was patented in the United States in 1974. It was initially used for testing the tolerance of chronic pain
Chronic pain
Chronic pain has several different meanings in medicine. Traditionally, the distinction between acute and chronic pain has relied upon an arbitrary interval of time from onset; the two most commonly used markers being 3 months and 6 months since the initiation of pain, though some theorists and...
patients to electrical stimulation before implantation of electrodes in the spinal cord dorsal column
Spinal Cord Stimulator
A spinal cord stimulator is a device used to exert pulsed electrical signals to the spinal cord to control chronic pain. Spinal cord stimulation , in the simplest form, consists of stimulating electrodes, implanted in the epidural space, an electrical pulse generator, implanted in the lower...
. The electrodes were attached to an implanted receiver, which received its power from an antenna worn on the surface of the skin. Although intended only for testing tolerance to electrical stimulation, many of the patients said they received so much relief from the TENS itself that they never returned for the implant.
A number of companies began manufacturing TENS units after the commercial success of the Medtronic
Medtronic
Medtronic, Inc. , based in suburban Minneapolis, Minnesota, is the world's largest medical technology company and is a Fortune 500 company.- History :...
device became known. The neurological division of Medtronic, founded by Don Maurer, Ed Schuck and Dr. Charles Ray, developed a number of applications for implanted electrical stimulation devices for treatment of epilepsy, Parkinson's disease, and other disorders of the nervous system. Maurer founded Empi, Inc., in 1977, and in the late 1980s purchased the TENS product line from Medtronic.
Today many people confuse TENS with Electro Muscle Stimulation (EMS). EMS and TENS devices look similar, with both using long electric lead wires and electrodes. TENS is for blocking pain, where EMS is for stimulating muscles.
Medical
TENS is a non-invasive, safe nerve stimulation intended to reduce pain, both acute and chronic. While controversy exists as to its effectiveness in the treatment of chronic pain, a number of systematic reviews or meta-analyses have confirmed its effectiveness for postoperative pain, osteoarthritis, and chronic musculoskeletal pain. Conversely, results from the Bone and Joint Decade 2000-2010 Task Force on Neck Pain, reported in early 2008, showed no clinically significant benefit to TENS for the treatment of neck pain when compared to placebo treatment. A January 2010, systematic literature search published in the journal Neurology, advised against recommending TENS for chronic low back pain since evidence is controversial for that type of pain. However, other reputable neurologists wrote in the same issue of the journal: "Absence of evidence is not evidence of absence," and although the research on TENS may be thin, "there seems to be considerable empirical evidence that, at least in some patients, TENS is useful." Recent clinical studies and meta-analysis suggest that having an adequate intensity of stimulation is necessary to achieve pain relief with TENS.Scientific studies show that high and low frequency TENS produce their effects by activation of opioid receptors in the central nervous system. Specifically, high frequency TENS activates delta-opioid receptors both in the spinal cord and supraspinally (in the medulla) while low frequency TENS activates beta-opioid receptors both in the spinal cord and supraspinally. Further high frequency TENS reduces excitation of central neurons that transmit nociceptive information, reduces release of excitatory neurotransmitters (glutamate) and increases the release of inhibitory neurotransmitters (GABA) in the spinal cord, and activates muscarinic receptors centrally to produce analgesia (in effect, temporarily blocking the pain gate). Low frequency TENS also releases serotonin and activates serotonin receptors in the spinal cord, releases GABA, and activates muscarinic receptors to reduce excitability of nociceptive neurons in the spinal cord.
In palliative care
Palliative care
Palliative care is a specialized area of healthcare that focuses on relieving and preventing the suffering of patients...
and pain medicine, TENS units are used in an attempt to temporarily alleviate neuropathic pain
Neuropathic pain
Neuropathic pain results from lesions or diseases affecting the somatosensory system. It may be associated with abnormal sensations called dysesthesia, which occur spontaneously and allodynia that occurs in response to external stimuli. Neuropathic pain may have continuous and/or episodic ...
(pain due to nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
damage).
Some patients benefit from this approach, while others do not, depending on individual differences,
and pain threshold. Use of TENS causes cell death at the site of application and should not be used long term. The number of cells that die is insignificant and most patients heal without complaints. TENS is more effective at relieving chronic pain, whereas when used on new injuries it sometimes aggravates the pain. Further use is documented in the attached references: in obstetric
Obstetrics
Obstetrics is the medical specialty dealing with the care of all women's reproductive tracts and their children during pregnancy , childbirth and the postnatal period...
care, particularly in labour
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
;
knee pain;
lithotripsy or bladder-stone removal;
and limb pain.
A significant number of TENS machine brands have been targeted for use for labour pain, although a 1997 report of a study done by the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...
said that TENS "has been shown not to be effective in postoperative and labour pain."
Safety
TENS electrodes should never be placed:- Over the eyes due to the risk of increasing intraocular pressureIntraocular pressureIntraocular pressure is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma...
- Transcerebrally
- On the front of the neck due to the risk of a acute hypotension (through a vasovagal reflex) or even a laryngospasmLaryngospasmIn medicine, laryngospasm is an uncontrolled/involuntary muscular contraction of the laryngeal cords. The condition typically lasts less than 60 seconds, and causes a partial blocking of breathing in, while breathing out remains easier. It may be triggered when the vocal cords or the area of the...
- Through the chest using an anterior and posterior electrode positions, or other transthoracic applications understood as "across a thoracic diameter"; this does not preclude coplanar applications
- Internally, except for specific applications of dental, vaginal, and anal stimulation that employ specialized TENS units
- On broken skin areas or wounds, although it can be placed around wounds.
- Over a tumour/malignancy (based on in vitroIn vitroIn vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
experiments where electricity promotes cell growth) - Directly over the spinal column
TENS should not be used across an artificial cardiac pacemaker
Artificial pacemaker
A pacemaker is a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart...
(or other indwelling stimulator, including across its leads) due to risk of interference and failure of the implanted device. Serious accidents have been recorded in cases when this principle was not observed. A 2009 review in this area suggests that eletrotherapy, including TENS, "are best avoided" in patients with pacemakers or implantable cardioverter-defibrillator
Implantable cardioverter-defibrillator
An implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation and ventricular tachycardia. The device is programmed to detect cardiac arrhythmia and correct it...
s (ICDs). They add that "there is no consensus and it may be possible to safely deliver these modalities in a proper setting with device and patient monitoring", and recommend further research. The review found several reports of ICDs administering inappropriate treatment due to interference with TENS devices, but notes that the reports on pacemakers are mixed: some non-programmable pacemakers were inhibited by TENS, but others were unaffected or auto-reprogrammed.
On areas of numb skin/decreased sensation TENS should be used with caution because it's likely less effective due to nerve damage. It may also cause skin irritation due to the inability to feel currents until they are too high. There's an unknown level of risk when placing electrodes over an infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
(possible spreading due to muscle contractions), but cross contamination with the electrodes themselves is of greater concern. TENS should also be used with caution in people with epilepsy or pregnant women; do not use over area of the uterus as the effects of electrical stimulation over the developing fetus are not known.
See also
- Action PotentialAction potentialIn physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
- Bio-Electric Stimulation TherapyBio-Electric Stimulation TherapyBio-Electric Stimulation Therapy , also known as micro current electro therapy , is a specific form of electrotherapy that delivers small amounts of current to the body. Current delivered is less than one milliAmpere, 100 times less than a typical TENS machine. BEST mimics what happens within...
- Electrical muscle stimulationElectrical muscle stimulationElectrical muscle stimulation , also known as neuromuscular electrical stimulation or electromyostimulation, is the elicitation of muscle contraction using electric impulses...
- Electroacupuncture/Percutaneous Electrical Nerve StimulationElectroacupunctureElectroacupuncture is a form of acupuncture where a small electric current is passed between pairs of acupuncture needles. Another term is Percutaneous Electrical Nerve Stimulation ....
- Electrotherapy (cosmetic)Electrotherapy (cosmetic)Cosmetic electrotherapy is a range of beauty treatments that uses low electric currents passed through the skin to produce several therapeutic effects, such as muscle toning in the body, and micro-lifting of the face...
- Failed back syndromeFailed back syndromeFailed back syndrome or post-laminectomy syndrome is a condition characterized by persistent pain following back surgeries.Failed back syndrome , also called "failed back surgery syndrome" , refers to chronic back and/or leg pain that occurs after back surgery. It is characterized as a chronic...
- MENSMENSA microcurrent electrical neuromuscular stimulator or MENS is a device used to send weak electrical signals into the body. Such devices apply extremely small electrical currents to nerves using electrodes placed on the skin...
- Neuromuscular dentistryNeuromuscular dentistryNeuromuscular dentistry is a dental treatment philosophy in which temporomandibular joints, masticatory muscles and central nervous system mechanisms are claimed to follow generic physiologic and anatomic laws applicable to all musculoskeletal systems. It is a treatment modality of dentistry that...
- Percutaneous tibial nerve stimulation
- Rebox electrotherapyRebox electrotherapyRebox electrotherapeutic method is based on non-invasive transcutaneous application of specific electric currents to a living tissue. Main indications for using the Rebox include treatment of acute and chronic pain, immobility, musculoskeletal and neurological disorders and oedema.- Method...
- Spinal stenosisSpinal stenosisLumbar spinal stenosis is a medical condition in which the spinal canal narrows and compresses the spinal cord and nerves at the level of the lumbar vertebra. This is usually due to the common occurrence of spinal degeneration that occurs with aging. It can also sometimes be caused by spinal disc...